Serpent possibly existing now (7)
I believe the answer is:
present
'existing now' is the definition.
(existing in the present day)
'serpent possibly' is the wordplay.
'possibly' indicates an anagram.
'serpent' anagrammed gives 'PRESENT'.
(Other definitions for present that I've seen before include "Gift; time now; here" , "Current" , "Christmas hand-out" , "show" , "Introduce formally" .)